Nuclear magnetic resonance has been shown to be a useful, non-perturbative tool for studying lipid bilayers. However, application to biological membranes has been limited by the broad line widths which are found for these systems. In these respects, biological membranes are similar to solids and methods which have been developed for solid state NMR can be used to study biological membranes. We propose to spin samples at the magic angle and use proton enhanced nuclear induction spectroscopy to obtain resolved NMR spectra for biological membranes. 31P and 13C NMR will be used to study the modes of interaction of cations with lipids. 13C NMR will be used to study the mechanism of selective cation transport by gramicidin channels in lipid bilayers. 15N NMR will be used to study the role of lysine residues in light induced proton translocation by bacteriorhodopsin. 13C and 2H NMR will be used to study carbohydrates associated with membrane lipids and proteins.